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  • mbenkerumass 6:00 am on January 20, 2020 Permalink | Reply
    Tags: Productivity   

    The Zeigenark Effect, Freeing Cognitive Resources 

    The Zeigenark Effect was outlined by early-twentieth century psychologist Bluma Zeigenark, who proposed and tested with experimentation that an incomplete task would dominate a certain level of cognitive attention, even when not focusing on said task. Obligations left unresolved, therefore are postulated to prevent one from accomplishing other, unrelated tasks. The remaining cognitive resources used for an incomplete task were termed the Zeigenark effect.

    Tasks that are left  incomplete, as you may know are virtually endless and most people tend to never run out of things they know they should be doing or will need to finish.

    zeigenark

    There is a way, however to ensure that the Zeigenark Effect is reduced, even without completing a task, giving one the ability to ignore the task to focus on other aspects of life. The method would be, as one comes to a close on their allotted time for concentration on said task, quickly produce a plan for how the incomplete task may later be completed, best done in writing. Through this method, one may free up cognitive resources to concentrate on other avenues of life and gain an edge whence returning to said incomplete task. If tasks are relatively uncomplicated but are many, one may decide to simply maintain a list of tasks, such that one need not use cognitive resources to stay on track.

     
  • mbenkerumass 9:00 am on January 19, 2020 Permalink | Reply
    Tags:   

    027/100 Shunt Reactance on Smith Chart 

    Example 3.5-2A: Measure the effect of susceptance on Smith Chart impedance matching.

    First, build the circuit and run the Smith Chart Matching tool.

    026-3

    A shunt capacitor moves in a clockwise direction across the smith chart tool:

    027-2

    Also note that a shunt inductor moves counter-clockwise across the smith chart tool:

    027-1

     
  • mbenkerumass 6:00 am on January 18, 2020 Permalink | Reply
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    Common Source JFET Amplifier 

    The advantages of using a Field Effect Transistor were discussed previously. The design of an amplifier using a junction field effect transistor (or another FET such as MOSFET) is generally the same procedure as that done for a BJT transistor amplifier.

    csa1csa2

     
  • mbenkerumass 2:35 pm on January 16, 2020 Permalink | Reply
    Tags: , Wireless Communications   

    Feed Lines (HAM Radio) 

    The following are questions that are used for the HAM Radio Technician level license. The title of this section of questions is: “Feel Lines: types of feed lines; attenuation vs. frequency; SWR concepts; matching; weather protections; choosing RF connectors and feed lines.”

    Question 1.

    Why is it important to have a low SWR in an antenna system that uses coaxial cable feed line?
    A. To reduce television interference
    B. To allow the efficient transfer of power and reduce losses
    C. To prolong antenna life
    D. All of these choices are correct

    SWR or Standing Wave Ratio refers to the efficiency of an antenna. A low SWR means that the loss will be reduced in the system. Therefore, the correct answer is B.

     

    Question 2.

    What is the impedance of the most commonly used coaxial cable in typical amateur radio installations?
    A. 8 ohms
    B. 50 ohms
    C. 600 ohms
    D. 12 ohms

    The correct answer is B. 50 Ohm transmission lines are very common in most RF systems. Television systems use 75 Ohm lines.

     

    Question 3.

    Why is coaxial cable used more often than any other feed line for amateur radio antenna systems?
    A. It is easy to use and requires few special installation considerations
    B. It has less loss than any other type of feed line
    C. It can handle more power than any other type of feed line
    D. It is less expensive than any other types of feed line

    The correct answer is A, considering it’s ease of use.

     

    Question 4.

    What does an antenna tuner do?
    A. It matches the antenna system impedance to the transceiver’s output impedance
    B. It helps a receiver automatically tune in weak stations
    C. It allows an antenna to be used on both transmit and receive
    D. It automatically selects the proper antenna for the frequency band being use

    An antenna tuners are used if the SWR is too high for a radio to operate properly. It matches the antenna’s impedance to the impedance of a transmitter. Automatic tuners also exist. Correct answer: A.

     

    Question 5.

    What generally happens as the frequency of a signal passing through coaxial cable is increased?
    A. The apparent SWR increases
    B. The reflected power increases
    C. The characteristic impedance increases
    D. The loss increases

    Coaxial cables work well within certain frequency ranges, however most are not rated to go above certain ranges. You’ll need to pay more for coaxial cable that can handle higher frequencies. The reason for them not working well at high frequencies is due to loss. Correct answer: D.

     

    Question 6.

    Which of the following connectors is most suitable for frequencies above 400 MHz?
    A. A UHF (PL-259/SO-239) connector
    B. A Type N connector
    C. An RS-213 connector
    D. A DB-25 connector

    Type N connectors are used above 400 MHz. Correct answer: B.
    N

     

    Question 7.

    Which of the following is true of PL-259 type coax connectors?
    A. They are preferred for microwave operation
    B. They are water tight
    C. They are commonly used at HF frequencies
    D. They are a bayonet type connector

    PL-259 type coax connectors are used in UHF, HF applications. Correct answer: C.pl259

     

    Question 8.

    Why should coax connectors exposed to the weather be sealed against water intrusion? A. To prevent an increase in feed line loss
    B. To prevent interference to telephones
    C. To keep the jacket from becoming loose
    D. All of these choices are correct

    The correct answer is A. Water intrusion can cause an increase in loss. Correct answer: A.

     

    Question 9.

    What might cause erratic changes in SWR readings?
    A. The transmitter is being modulated
    B. A loose connection in an antenna or a feed line
    C. The transmitter is being over-modulated
    D. Interference from other stations is distorting your signal

    Standing wave ratio is important for the measuring the efficiency of equipment. Modulation or interference therefore will not have an effect on the SWR. Loose connections may however cause an issue with SWR. Correct answer: B.

     

    Question 10.

    What electrical difference exists between the smaller RG-58 and larger RG-8 coaxial cables?
    A. There is no significant difference between the two types
    B. RG-58 cable has less loss at a given frequency
    C. RG-8 cable has less loss at a given frequency
    D. RG-58 cable can handle higher power levels

    RG-58 and RG-8, although similar are different in that the RG-8 coax cable has less loss per length. Correct answer: C. The following table lists losses per feet:

    coax1

     

     

    Question 11.

    Which of the following types of feed line has the lowest loss at VHF and UHF?
    A. 50-ohm flexible coax
    B. Multi-conductor unbalanced cable
    C. Air-insulated hard line
    D. 75-ohm flexible coax

    Air-insulated hard line coax has the lowest loss with added insulation. Correct answer: C.

     
  • mbenkerumass 6:00 am on January 15, 2020 Permalink | Reply
    Tags:   

    Microstrip Double-Stub Load Matching 

    The following matches a 50 Ohm line to a 100 Ohm load at 10 GHz using a double-stub component. This was designed using the ADS passive circuit DesignGuide tool. This method is a great alternative to using the Smith Chart matching tool for lumped elements if you need a microstrip line for matching.

    Circuit:

    dsmat1

    Substrate:

    dsmat2

     

    Momentum simulation result (can be tuned to center better at 10 GHz):

    dsmat3

    Layout component:

    dsmat4

     

     

     
  • mbenkerumass 9:00 am on January 14, 2020 Permalink | Reply
    Tags: ,   

    Ray Optics – Graded-Index Fibers, Matrix Optics 

    Graded-Index Fibers

    Guiding light rays with multiple lenses or mirrors is possible, however this may result in great loss of optical power due to refraction in a system if there are many lenses or mirrors. Using total internal reflection however, rays may be transmitted over long distances without these losses. Glass fibers are the primary choice for guiding light in this manner using total internal reflection. Glass fibers consist of a glass wire with a cladding. The refractive index of the outer cladding will be smaller than the glass core. This allows for a consistent total internal reflection throughout the wire.

    fiber

    A graded-index material (GRIN) has a refractive index that varies throughout the material. When a ray moves through a graded-index material, the variance in refractive index causes the ray to bend and curve according to how the graded index is laid out.

    grinparax

    The path of an optical ray in graded-index material is determined by Fermat’s principle, which states that the path of a ray is the integral of the refractive index (a function of position on the material) between two points, equated to zero. The ray equation can solve this problem, however for simplification, a paraxial approach is taken to give the paraxial ray equation.

    Ray Equation:

    rayeq

    Paraxial Ray Equation:

    rayeqpar

    A graded index glass fiber is modeled below:

    gribfiber


     

    Matrix Optics

    A paraxial ray is described by a coordinate and angle. Using this approximation, the output paraxial ray going through a system can be written in matrix form:

    abcd          ,            abcd1

    An optical system can be modeled using the 2×2 ABCD matrix. Matrices of systems may also be cascaded to describe the effect of many systems on a ray.

    abcdmatricies

     
  • mbenkerumass 9:00 am on January 12, 2020 Permalink | Reply
    Tags:   

    026/100 Lumped Element Smith Chart Movements: Series Inductor 

    Example 3.5-1: Measure the amount of movement caused by the reactance added to the circuit below. Measure the change from the starting point to the end point on the Smith Chart.

    026-1

    The circuit simulated gives the following result:

    026-2

    Recall that the circuit without a series inductor had the following result:

    025-3

    Through this simulation, it is shown that adding a series inductor causes the smith chart diagram plot to move in a clockwise direction.

    Note the change using the Smith Chart matching tool:

    026-3026-4

     

     
  • mbenkerumass 7:00 am on January 11, 2020 Permalink | Reply
    Tags: , Transistors   

    BJT vs. FET 

    Transistors are important components that are used in a variety of applications. Some types can be used for switching, some for amplification or both. Other transistors perform exclusive tasks, such as the phototransistor, which responds to light by producing a current.

    The main premise of a transistor is that by feeding a transistor a source voltage or current (depending on the type), the transistor allows for the passage of electrons. This process is accomplished through pnp or npn semiconductor structures. The following diagrams provide a general example of the function of a transistor:

    t4t2

    transistor

    t3

     

     

    Bipolar Junction Transistors (BJT) are controlled using a biasing current at the base pin. This means that they will also consume more current than other transistors such as the FET. One advantage of BJT transistors is that they offer greater output gain than an FET. However, BJT can be much larger in size than FET and for this reason, they are less popular, despite being easier to manufacture.

    bjt

    Field Effect Transistors (FET) are voltage-controlled. For this reason they essentially draw no current and therefore do not pose a substantial load to a circuit. FETs are not as useful for gain as BJT, however if the intent is not for amplification then this is not a problem. FETs can be manufactured very small and this is important in manufacturing integrated circuits that use many transistors. FETs and especially the MOSFET subtype are more expensive to manufacture, but remain more popular than the BJT.

    fet

    Some FET transistor types are even constructed on the nano-scale. The FinFET for example is about 10 nm, currently used by Intel, Samsung and others.

    FinFET size

    (2)

    http://www.learningaboutelectronics.com/Articles/Types-of-transistors.php

     
  • mbenkerumass 6:00 am on January 8, 2020 Permalink | Reply
    Tags: ,   

    Microstrip Zig-Zag Passband Filter 

    zzf1zzf2zzf3

     
  • mbenkerumass 9:00 am on January 7, 2020 Permalink | Reply
    Tags: ,   

    Planar Boundaries, Total Internal Reflection, Beamsplitters 

    Refraction is an important effect in ray optics. The refractive index of a material influences how rays react when entering or leaving a boundary. For instance, if the ray is exiting a medium of smaller refractive index and entering a medium with a higher refractive index, the angle will tend towards being perpendicular to the boundary line. The angle of refraction is also greater than the angle of incidence. This case is called external refraction (n1 < n2) and (θ1 > θ2). If the ray is exiting a medium of higher refractive index into a medium with a lower refractive index, the rays will tend towards being closer to parallel with the medium boundary. This case is referred to as internal refraction (n1 > n2) and (θ2 > θ1). Both of these situations are governed by Snell’s Law:

    n1*sin(θ1) = n2*sin(θ2)

    When the rays are paraxial, the relation between θ1 and θ2 is linear (n1*θ1 = n2*θ2).

    refraction

    The critical angle occurs when n1*sin(θ1) = n2*sin(pi/2) = n2. θ1 in this case is then equal to the critical angle. If θ1 is greater than the critical angle θC, refraction cannot occur and the situation is characterized by a phenomenon known as total internal reflection (TIR). Total internal reflection is the basis for many optical systems and devices. Systems with total internal reflection are understood to be highly efficient even under more rigorous approaches to optics such as electromagnetic optics.

    tir

     

    Prisms are common applications of refraction. A prism of apex angle α and refractive index n deflects a ray incident at an angle of θ:

    prism2

    This is taken by using Snell’s law twice along two planar boundaries.

    prism1

     

    A beamsplitter is an optical component that divides a ray into a reflected and refracted (or transmitted) ray. The proportions of reflected to refractive light is a problem dealt with in electromagnetic optics. Beamsplitters are also used to combine two rays.

    beamsplit

    Beam directors apply Snell’s law and the rules governing refraction to direct rays in different directions. Three methods of directing waves are the biprism, the Fresnel biprism and the axicon.

     

     

     
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